Relief valve for power transmissions



Nov. 1, 1938. ELRQS 2,134,803

RELIEF VALVE FOR POWER TRANSMISSIONS Filed Nov. e, 1955 INVENTQR Elm 0v4:90:45

ATTORNEY Patented Nov. 1, 1938 PATENT OFFICE RELIEF VALVE FOR POWERTRANSDHS- SIGNS Edwin L. Rose, Water-town, Conn... assignor to TheWaterbury Tool Company. Waterbury, Conn a corporation of ConnecticutApplication November 6, 1936, Serial No. 109,553

11 Claims.

In transmissions of this character it is necessary to provide means forlimiting the pressure developed in the high pressure side of the systemand for this purpose a spring-loaded relief valve is customarilyemployed. In transmissions operating at high pressures, say of the orderof two thousandpounds per square inch, it-is necessary, if the valve isof the size to carry the full pump discharge, either to employ anexcessively large heavy spring or to provide means for partiallybalancing thefluid pressures acting on the valve member. By providingbalancing means, such as a piston subject to fluid pressure forcestending to close the valve and having an area only slightly smaller thanthe area on the valve exposed to fluid pressure forces tending to openthe valvepa comparatively small spring is sufficient to hold the valveclosed against very high pressures. It has been found, however, thatwith a valve of this character which is correctly designed for thestatic pressure forces exerted on the valve, satisfactory operation cannot be obtained due to the effect of dynamic pressure forces whichappear as soon as the valve begins to open. ,Thus it frequently occursthat a valve .-of this character will open a small distance, far

short of its required full opening, and due to pressure drops caused byhigh velocity flow adjacent the opening will come into equilibrium andprevent further opening of the valve except at an increased pressure.

a It is an object of the present invention to-provide a pressurelimiting means forpower transmissions of the character describedincluding a spring-loaded relief valve which is provided with a pistonfor balancing a substantial portion of the static pressure forcestending to open the valve and which is also provided wlth'means forbalancing the dynamic pressure forces at all de grees of valve opening.

A further objectis .to provide a relief valve capable of passing thefull discharge of the pump of the power transmission and operative V tomove from a very small opening to full opening without requiring asignificant increase in pressure; inothe'r words,- to provide-a reliefvalve ingwhlch the pressure at which it operates is independent. of thequantity discharged .through the valve.

Further objects and advantages of the presentinvention will be, apparentfrom the following description, reference being had to the. sacrumpanying drawing wherein a preferred form of the presentinvention isclearly shown.

In the drawing:

Fig. 1 is a fragmentary cross sectional 'view of a relief valvemechanism incorporating a preferred form of the present invention.

Fig. 2 is a cross section .on line 2- -2 of Fig. l. v

Fig. 3 is a diagrammatic view of a fluid pressure energy translatingdevice incorporating the present invention.

Fig. is a fragmentary sectional view corresponding to a portion of Fig.1 with the parts I in a different position.

In the form of the invention illustrated in the drawing a fluid pressureenergy translating device I!) may be of any suitable construction, andis illustrated as of the well-known "Waterbury type, comprising arevolving cylinder barrel l2 having bores within which pistons arereciprocated through the medium of a'socket ring and tilting boxassembly I4. The assembly I4 ismounted for angular adjustment ontransverse trunnions l5. Each of the cylinders of the barrel I2 has aport l6 which alternately registers with an arcuate delivery port l8 anda corresponding arcuate suction port 20 formed in a valve plate 22.Suction and discharge conduits 24 and 26 connect with the ports 20 andI8, respectively. The valve plate 22 isformed with a branch conduit 28connecting withv the port it and a branch conduit 30 connecting with theport 20. A transverse bore 32 connects the conduits 28 and 30 and withthem forms a bypass conduit connecting the ports l8 and 20. Within thebore 32 is mounted a relief valve 34, which is illustrated in detail inFigs. 1 and 2. The port 20 connects with a transverse bore 36 withinwhich is located a ball check valve 38 forming a re-' plenlshing valvefor the. suction side of the device.

Referring now to Figs. 1 and 2, the valve 34 comprises a poppet valvehead Ill-having a conical seating surface 42 coacting with acorresponding conical seating surface 44 formed .in the bore 32. Thebore 32 has a portion 46 of reduced diameter at its right-hand end andhas an enlarged portion 48 to the left of the-seat 44. The head 40 isrigidly secured to a stem '50 by a retainingnut 52. The stem 50 carriesat its right-hand end a piston portion 54 slidably engaged in thereduced portion 46 of the bore 32.

. Adjacent the head 40 the stem carries a shroudor sleeve I" which ismounted by a press or shrink-flt on flns integral with stem 50.

The left-hand edge of the shroud It is beveled as indicated at It whilethe right-hand face of the head ll is provided with an annular groove ofa V-shaped cross section as at 02. There is thus provided a path forfluid passing through the valve which is generally a-shaped as willbeseen from Fig. 4 so that before between the seating surfaces of thevalve, the fluid is reverledaxiallyinitsdirectionofflow. Theseatingsurface 42 of thehead I is also provided with an annular groove orpocket 64 near the outer edge of the seat I! for the purpose of causingturbulence beiore the stream of fluid leaves the valve seating surfaces.The valve BI is normally held to the right by a spring ll urging thesurfaces]! and 44 into contact. A central bore" provides communicationbetween the chambers at opposite has to overcome. With the tilting boxIt adjusted for acomparatively small pump discharge only a small openingat the valve 42- is necessary to passthefulldischarge of thepumpatthis'set gg ting. If the pressure in the port It rises beyond thedesired maximum value, which is determined by the force of the springII, this static pressure is exerted on the valve it over the right-handface of the head 42 in a direction tending to open the valve and overthe left-hand end face of the piston 84 in a direction tending to closethe valve. Since the area of the former face is slightly larger than thearea of the latter, the resultant force is in a direction tending toopen the valve and when its magnitude exceeds the force of the spring60, the valve It moves to the left permitting fluid to pass between thesurfaces 42 and u.

At a small valve opening, suchas illustrated in Pig. 1, the velocity offlow from conduit 28 through bore 82 and through the space between theshroud II and stem II and between the end faces ll and ti is low.

surfaces 42 and 44 takes place at extremely high velocities. however,due to the steep pressure gradient which must be produced across thesesuri'aces. In the space adjacent the entering edge of the surfaces 42and M, the fluid velocitybeglns to increase and a certain amountofpressure drop occurs in the fluid adjacent the head 40 immediatelybefore entering the space between the surfaces 42 and M. In order toinsure that this pressure drop does not disturb the predetermined staticunbalance of the valve, the groove 84 forms a pocket adjacent the outletfrom the valve seating surface to cause turbulent flowat this point.

quantity up to the maximum pulp The flow between the flow conditionswill be the same as those for static conditions when the valve isclosed.

With the tilting box it adjusted for a, large pump discharge, therelative effect of the groove 84 decreases so that it becomessubstantially negligible at full discharge. This condition is 11'-lustrated in Fig. 4 from which it will be seen that the cross section ofthe path between the surfaces 42 and 44 is substantially equal to thatbetween the end face 60 of the shroud I6 and the annular groove 62 ofthe head ll. Under these conditions at full valve opening, the velocitybetween the faces 60 and 62 is of the same order of magnitude as thatbetween the seating surfaces 42 and 44. In order to escape through thevalve the fluid must be reversed in its direction of flow twice beforeleaving the valve. The pressure drops which are created on the end faceof the head 4. by high velocity flow adjacent the same are thuscompensated or canceled out so that the resultant force acting on thevalve is substantially the same as that under static pressureconditions. As a result of the compensation for velocity effect both atthe small and large valve openings, the valve 50 opens at the samepressure regardless of the quantity of fluid which must be by-passed inorder to prevent a further rise in pressure. Thus, any discharge may belay-passed through the valve 4 at a fixed pressure.

While the form of embodiment of the invention as herein disclosed,constitutes a preferred form,

it is to be understood that other forms might be adopted, all comingwithin the scope of. the claims which follow.

What is claimed is as follows:

1. In a fluid pressure device having a pair of conduits one of which issubject to high pressure while the other is subject to a low pressure,the combination of means forming a by-pass conduit between said pair ofconduits, a valve normally closing said'by-pass conduit and having .ahead subject to pressure tending to open the valve and an opposedbalancing piston subject to pressure tending to close the valve, ashroud surrounding the valve near the head and forming with the head apassage through which fluid must pass to escape through the valve; saidpassage being formed to cause a reversal in the direction of fluid flowaxially immediately before the fluid flows through the valve opening,

- 2. In a fluid pressure device having a pair of conduits one of whichis subject to high pressure while the other is subject to a lowpressure, the combination of means forming a by-pass conduit betweensaid pair of conduits, a valve normally .closing said by-pass conduitand having a head subject to pressure tending to open the valve and anopposed balancing piston subject to pressure tending to close the valve,a shroud surrounding the valve near the head and forming with the head apassage through which fluid must pass to escape through the valve, saidpassage being formed to provide a generally S-shaped path for fluid flowat the valve opening when viewed in longitudinal section.

3. In a fluid pressure device having a pair of conduits one of which issubject to high pressure while the other is subject to a low pressure,the combination of means forming a by-pass conduit between said pair 'ofconduits, a valve normally closing said by-pass conduit and having a hesubject to pressure tending to open the valve and an opposed balancingpiston subject to pressure tending to close'the valve, means near thehead 76 iorming with the head a passage through which fluid must pass toescape through the valve, said passage being formed ,to cause a reversalin the direction of fluid flow axially immediately before the fluidflows through the valve opening.

a. In a fluid pressure device having a pair of conduits one of which issubject to high pressure while the other is subject to a low pressure,the

combination of means forming a by-pass conduit between said pair ofconduits, a poppet valve normally closing said by-pass conduit andhaving a head subject to pressure tending to open the valve, an opposedbalancing piston connected with the head and subject to pressure tendingto close the valve, and means formed in one of the cooperating seatingsurfaces of the valve for.breaking up the continuity of flow at smallvalve openings to produce a back pressure at the valve opening tendingto ofiset the pressure drop resulting from high velocity flow adjacentthe head.

5. In a fluid pressure device having a pair of conduits one of which issubject to high pressure while the other is subject to a low pressure,the combination of means forming a bypass conduit between said pair ofconduits, a poppet valve normally closing said by-pass conduit andhaving a head subject to pressure tending to open the valve,

an opposed balancing piston connected with the head and subject topressure tending to close the valve, means for causing a reversal offluid flow in an axial direction prior to entering the valve opening,and effective to offset a velocitypressure drop at the large valveopenings, and means for interrupting flow continuity through the valveopening and effective to ofiset avelocity pressure drop at the smallvalve openings.

. 6. In a fluid pressure device having a pair of conduits one of whichis subject to high pressure while the other is subject to a lowpressure, the

edcombination of means forming a by-pass conconduits one of which issubject to high pressure while the other is subject to a low pressure,the combination 01' means forming a by-pass conduit between said pair ofconduits, a poppet valve norinally closing said by-pass conduit andhaving a head subject to pressure tending to open the valve, an opposedbalancing piston connected with the head and subject to pressure tendingto close the valve, and means for balancing the velocity head forming apassage through which fluid must pass to escape through the valve, saidpassage being formed to cause a reversal in the direction of fluid flowaxially immediately before the fluid flows through the valve opening.

9. In a fluid pressure device having a high pressure conduit, meansforming a conduit through which pressure fluid may be relieved from thefirst conduit to a point of lower pressure, a poppet valve normallyclosing said last conduit and having a head subject to pressure tendingto open the valve, an opposed balancing piston connected with the headand subject to pressure tending to close the valve, and means formed inone of theme}:- erating seatingsurfaces of the valve for breaking up thecontinuity of flow at small valve openings to produce a back pressure atthe valve opening tending to oflset the pressure drop resulting fromhigh velocity flow adjacent the head.

10. In a fluid pressure device having a high pressure conduit, meansforming a conduit through which pressure fluid may be relieved from thefirst conduit to a point of lower pressure, a poppet valve normallyclosing said last conduit and having a head subject to pressure tendingto open the valve, an opposed balancing piston connected with the headand subject to pressure tending to close the valve, means for causing areversal of fluid flow in an axial direction prior to entering the valveopening, and effective to offset a velocity pressure drop at the largevalve openings, and means for interrupting flow continuity through thevalve opening and effective to offset a velocity pressure drop at thesmall valve openings;

11. In a fluid pressure device having a high pressure conduit, meansforming a conduit through which pressure fluid may be relieved from thefirst conduit to a point of lower-pressure, a poppet valve normallyclosing said last conduit and having a head subject to pressure tendingto open the valve, an opposed balancing piston connected with the headand subject to pressure tending to close the valve, and means forbalancing the velocity pressure drops eflective at the valve head at anydegreecof opening.

' EDWIN L. ROSE.

